Note: Descriptions are shown in the official language in which they were submitted.
CA 02242081 1998-06-26
COOLING CONTROL SYSTEM AND
COOLING CONTROL METHOD FOR ENGINE
BACKGROUND OF THE INVENTION
~ 1. FIELD OF THE INVENTION
This invention relates to a cooling control system and a cooling control
method for cooling an engine of, for example, a vehicle, more particularly, to acooling control system and method capable of enhancing the responsibility of
a temperature control with respect to cooling medium circulated in the engine
and improving the control precision.
2. DESCRIPTION OF THE RELATED ART
In an engine used in a vehicle or the like, a water cooling type cooling
device using a radiator is generally used for cooling the engine.
In this type of the cooling device, a thermostat is used in order to
control temperature of the cooling water. When temperature of the cooling
water is lower than a predetermined temperature, the cooling water is
circulated in a bypass not to flow into the radiator with the action of the
thermostat.
Fig. 29 shows the above structure, in which numeral 1 is an engine
composed of a cylinder block la and a cylinder head lb, and a fluid conduit
illustrated with Arrow c is formed in the cylinder block la and the cylinder
head lb of the engine 1.
Numeral 2 is a heat exchanger, namely a radiator. A fluid conduit 2c
is formed in the radiator 2 as well-known, and a cooling-water inlet portion 2a
and a cooling-water outlet portion 2b of the radiator 2 are connected to a
cooling-water conduit 3 circulating the cooling water between the engine 1
and the radiator 2.
The cooling-water conduit 3 is composed of an outflow-side cooling-
water conduit 3a linking from an outflow portion ld of the cooling water,
CA 02242081 1998-06-26
placed in the upper portion of the engine, to the inflow portion 2a of the
cooling water placed in the upper portion of the radiator 2; an inflow-side
cooling-water conduit 3b linking from the outflow portion 2b of the cooling
water, placed in the lower portion of the radiator 2, to an inflow portion le of5 the cooling water placed in the lower portion of the engine 1; and a bypass
conduit 3c connecting the conduits 3a and 3b to each other.
In a branch portion between the outflow-side cooling-water conduit 3a
and the bypass conduit 3c in the cooling-water conduit 3, a thermostat 4 is
disposed. The thermostat 4 is provided therein with a thermal expansive body
10 (e-g- wax) expanding and shrinking with ch~ngin3~ of temperature of the
cooling water. When the cooling-water temperature is high (e.g. over 80 ~C),
the valve is opened by the expansion of the thermal expansive body so that the
cooling water flowing from the outflow portion ld of the engine 1 flows
through the outflow-side cooling-water conduit 3a into the radiator 2. The
15 cooling water cooled in the radiator 2 and dissipating heat is operated to flow
from the outflow portion 2b through the inflow-side cooling-water conduit 3b,
and through the inflow portion le of the engine 1 into the engine 1.
When the temperature of the cooling water is low, the valve of the
thermostat 4 is closed by the shrinkage of the thermal expansive body, so that
20 the cooling water flowing from the outflow portion ld of the engine 1 flows
through the bypass conduit 3c, and through the inflow portion le of the engine
into cooling pipes c of the engine 1.
In Fig. 29, numeral S is a water pump disposed in the inflow portion le
of the engine 1, of which the rotating shaft is rotated by the rotation of a
25 crank-shaft (not shown) of the engine 1, so that the cooling water is forcibly
circulated. Numeral 6 is a fan unit for forcibly blowing cooled air into the
radiator 2, and composed of a cooling fan 6a and a fan motor 6b rotationally
driving the cooling fan 6a.
The valve opening and the valve closing actions by the thermostat are
30 determined by the temperature of the cooling water, and also by the expansion and shrinkage of the thermal expansive body such as wax, therefore the
temperature in the valve opening and the temperature in the valve closing are
CA 02242081 1998-06-26
not constant. The thermal expansive body such as wax takes some time to
operate the valve after receiving the changing of the temperature of the coolingwater until. Especially, the responsibility during the decrease of the
temperature is inferior as compared with that during the increase of the
temperature, that is to say it has hysteresis properties. As a result, there is a
technical disadvantage in which the cooling water is not easily adjusted to be
in a constant temperature required.
It is proposed that the flow of the cooling water is electrically
controlled not to harness the actions of opening and closing valve by the
10 thermal expansive body such as wax.
This is, for example, the control of a rotational angle of a butterfly
valve using a stepping motor. Omitting the thermostat 4 shown in Fig. 29, a
valve unit 7 provided with the butterfly valve instead of the thermostat 4 is
disposed in the outflow-side cooling-water conduit 3a as illustrated with a longdashed line in Fig. 29.
Fig. 30 shows an example of the above valve unit 7, in which a circular
plane shaped butterfly valve 7a is supported in the cooling-water conduit 3a to
be rotated by a shaft 7b. A worm wheel 7c is attached on an end of the shaft
7b, and a worm 7e inserted in a rotational drive shaft of a motor 7d is engaged
20 wlth the worm wheel 7c.
The motor 7 is supplied with the operation current for rotating the
drive shaft thereof in the forward and reverse directions by a control unit
(ECU) controlling the operation condition of the overall engine. Therefore,
when the current for rotating the drive shaft in the forward direction is passed25 into the motor 7d by the action of the ECU, the shaft 7b of the butterfly valve
7a is rotated in one direction by a well-known decelerating action produced by
the worm 7e and the worm wheel 7c, whereby the plane direction of the
butterfly valve 7a is rotated in the same direction as the flowing direction of
the cooling-water conduit 3a, resulting in the valve opening state.
On the other hand, when the current for rotating the drive shaft in the
reverse direction is passed into the motor 7d by the action of ECU, the shaft
7b of the butterfly valve 7a is rotated in the other direction, whereby the plane
CA 02242081 1998-06-26
direction of the butterfly valve 7a is rotated in a direction perpendicular to the
flowing direction of the cooling-water conduit 3a, resulting in the valve closing
state.
The ECU receives information such as the temperature of the cooling
water in the engine, and controls the temperature of the cooling water by
controlling the aforementioned motor with the use of the above information.
In addition, in response to a control signal from the control unit (ECU)
fetching various operational parameters which are detected from the engine, a
stepping motor (not shown) rotating the butterfly valve is driven so as to
lo control the flow of the cooling water flowing toward the radiator.
In the cooling control system using the butterfly valve as described
thus far, a temperature detecting element such as a thermistor (not shown) is
disposed in a part of the pipes for the cooling water in the engine 1, and the
motor 7d is driven responsive to the temperature of the cooling water detected
15 by the temperature detecting element.
According to the structure as described above, the effects of the
hysteresis properties seen in the former example using the thermostat including
the thermal expansive body is decreased somewhat.
After the temperature detecting element senses the ch~nging of the
20 temperature of the cooling water, however, the ECU controls an angle of the
valve on the basis of the sensed ch~nging, that is to say it is a follow-up
control. In consequence, in this point both examples are the same.
Even the cooling control system using the butterfly valve in the latter
example cannot escape having a hunting phenomenon which is the temperature
25 of the cooling water is changed around a specific temperature Tc at all times,
resulting in the difficulty of the control with stability and high precision.
Generally, when an engine for a vehicle is driven in a high temperature
state before overheating, fuel economy is enhanced and the generation of a
poisonous gas is reduced.
When the aforementioned hunting occurs, in order to avoid the worst
state of the overheating of the engine, the aforementioned temperature Tc of
the cooling water should be adjusted to be lower, thereby creating a technical
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disadvantage of sacrificing fuel economy.
Where an actuator to rotate the aforementioned butterfly valve is
concerned, for example, the stepping motor is provided therein as described
hereinbefore, and driven by the pulse control signal caused by ECU, thereby
rotating the butterfly valve.
The m~imum rotational speed (rpm/min) of the aforementioned type
of the stepping motor is extremely lower on the action thereof than that of a
direct-current motor as is well-known. Therefore, when it is structured to
obtain predetermined rotation torque using the aforementioned worm gear or
10 another decelerating gear, and to afford the appropriate rotational speed to the
butterfly valve, the motor itself is inevitably requied to have high torque,
resulting in a technical disadvantage in that the overall actuator is larger in size.
Moreover, for example, in occurring any failure in the motor or
damage of the aforementioned decelerating gear, the operation of opening and
15 closing the butterfly valve results in impossibility. For example, when the
above failure or damage occurs in a state that the butterfly valve is closed or is
nearly closed at a half open angle, the engine is cooled insufficiently, therebyhaving a technical disadvantage in that the engine is overheated without being
noticed by a driver.
The present invention is performed in order to resolve the technical
disadvantages described thus far. It is an object of the present invention to
provide a cooling control system and a cooling control method having the
improved control precision in which temperature is conducted in a state that
the ch~ngin~ of temperatures of the cooling water is forecast, and the
25 aforementioned hunting does not occur.
It is another object of the present invention to provide a cooling control
system capable of exploiting a fail-safe function and previously avoiding
disadvantages such as the overheat of an engine, controlled by ~l~m~ging a
part of a drive device of a flow control valve or the like.
In the structure in which the valve unit 7 is controlled by the stepping
motor after receiving the control signal from the ECU as described above,
there may be cases where an opening sensor for detecting the degree of valve
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opening (not shown) as well as the stepping motor rotationally driving the
butterfly valve is needed. This needs adoption of a complicated control
system, for example, the stepping motor is driven by retllrning the information
of the opening sensor to the ECU, resulting in high costs.
The present invention is carried out in order to resolve the
aforementioned technical disadvantage, and is characterized in that the degree
of butterfly-valve opening is controlled with a thermo-element enclosing a
thermal expansive body such as wax, and the thermal-element is forcibly
operated by a heater to respond thermally. Therefore, it is an object of the
10 present invention to provide a cooling control system capable of improving the
responsibility of a temperature control for cooling water and the control
precision at small cost.
SUMMARY OF THE INVENTION
A cooling control system for an engine according to the present
invention carried out for resolving the aforementioned disadvantages, in which
a circulating passage of a cooling medium is formed between a fluid conduit
20 formed in the engine and a fluid conduit formed in a heat exchanger, and heatgenerated in the engine is dissipated with the heat exchanger by circulating thecooling medium in the circulating passage, includes: a flow control means for
controlling the flow of the cooling medium in the circulating passage between
the engine and the heat exchanger in accordance to the degree of valve
25 opening; an information extracting means for extracting at least load
information in respect of the engine and temperature information of the cooling
medium; and a control unit finding a target setting temperature of the cooling
medium on the basis of the load information, and finding a temperature
deviation of the temperature information of the cooling medium from the target
30 setting temperature, and generating a control signal for an actuator of the flow
control means on basis of the relationship between the temperature deviation
and a changing velocity of the temperature deviation.
CA 02242081 1998-06-26
In this case, the load information is generated from at least engine
speed and information of the degree of throttle-valve opening.
It is structured that the control unit operates a first control signal
generating mode for generating a control signal for the actuator when the
5 temperature deviation and the ch~n~n~ velocity of the temperature deviation
are below predetermined values, and a second control signal generation mode
for generating a control signal for the actuator when the temperature deviation
and the ch~nging velocity of the temperature deviation exceed predetermined
values.
In this point, it is preferably structured that the first control signal
generating mode includes an integral control element continuously and slightly
ch~nging the flow of the cooling medium, controlled by the flow control means,
at unit-times in response to the temperature deviations; and the second control
signal generating mode generates the control signal for the actuator on the
15 basis of flow setting data of the cooling medium which is read out from a mapwritten to correspond with the temperature deviation and the ch~nging velocity
of the temperature deviation.
In a further preferred embodiment, a sensor showing the flow of the
cooling medium controlled by the flow control means is included, in which
20 information obtained from the sensor is used for a computing process in the
control unit.
In the preferred embodiment, the flow control means comprises a
butterfly valve which is disposed in a tubular cooling-medium conduit and of
which an angle in the plane direction is changed with respect to a flowing
25 direction of the cooling medium; and the sensor showing the flow of the
cooling medium is an angle sensor generating information in respect of a
rotational angle of the butterfly valve.
In the preferred embodiment, it is structured that the actuator includes
a direct-current motor driven to be rotated on the basis of the control signal
30 outputted from the control unit, a clutch mechanism transferring and releasing
a rotational driving force of the direct-current motor, and a deceleration
mechanism decelerating rotational speed of the direct-current motor through
CA 02242081 1998-06-26
the clutch mechanism, and the flow control means is provided with a return
spring propelling the flow control means in the direction of valve opening.
The clutch mechanism receives an abnormal condition output and turns
a released state so that the flow control means holds a valve opening state with5 the return spring.
A cooling control method for an engine according to the present
invention carried out in order to resolve the aforementioned disadvantages, in
which a circulating passage of a cooling medium is formed between a fluid
conduit formed in the engine and a fluid conduit formed in a heat exchanger
10 and heat generated in the engine is dissipated with the heat exchanger by
circl1l~ting the cooling medium via a flow control means in the circulating
passage, is characterized by including: a step of fetching at least load
information in respect of the engine and temperature information of the cooling
medium; a step of finding a target setting temperature of the cooling medium
15 on the basis of the load information; a step of finding a temperature deviation
of the temperature information of the cooling medium from the target setting
temperature; a step of computing the temperature deviation and a ch~np.ing
velocity of the temperature deviation; a step of generating a control signal foran actuator of the flow control means on basis of the relationship between the
20 temperature deviation and the ch~nging velocity of the temperature deviation;and a step of driving the actuator on the basis of the control signal and
operating the flow control for the cooling medium flowing into the heat
exchanger.
In this case, preferably, a step of determining whether or not the
25 temperature deviation and the ch~nging velocity of the temperature deviation
are below predetermined values is further added in the step for generating the
control signal to drive the actuator, and when the values of the temperature
deviation and the ch~nginp velocity of the temperature deviation are
determined to be below the predetermined values, a step of generating the
30 control signal including an integral control element continuously and slightly
changing the flow of the cooling medium, controlled by the flow control means,
at unit-times in response to the temperature deviations is performed, and when
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the values of the temperature deviation and the ch~n~ing velocity of the
temperature deviation are determined not to be below the predetermined
values, a step of generating the control signal on the basis of flow setting data
of the cooling medium which is read out from a map written to correspond
with the temperature deviation and the ch~nging velocity of the temperature
deviation is performed.
According to the structure and the control method described thus far,
the target setting temperature of the cooling water as the cooling medium is
defined on the basis of, for example, the load information obtained from the
10 engine speed and the angle information of the throttle valve. The temperaturedeviation is found at predetermined unit of time from the target setting
temperature and the temperature information of the cooling water, and also the
ch~nging velocity of the temperature deviation is found.
The control signal is generated with the temperature deviation and the
15 ch~nging velocity of the temperature deviation as parameter, and sent to the
actuator driving, for example, the butterfly valve as the flow control means.
In this case, the generating mode for the control signal is changed in
accordance to values of the temperature deviation and the ch~nging velocity of
the temperature deviation, and when the values of the temperature deviation
20 and the ch~nging velocity of the temperature deviation are less than
predetermined values, the rotational angle of the butterfly valve is controlled
by a PI control including the integral control element that changes the flow of
the cooling water at unit-times continuously and slightly.
When the values of the temperature deviation and the ch~nging
25 velocity of the temperature deviation exceeds the predetermined values, a
quick response control for driving the butterfly valve quickly is performed on
the basis of the flow setting data of the cooling medium which is read out from
a map written to correspond with the temperature deviation and the ch~nging
velocity of the temperature deviation.
As a result, the temperature is conducted in the state in which the
ch~nging of the temperatures of the cooling water is forecast, and with using inconjunction with the aforementioned PI control, the control decision capable
CA 02242081 1998-06-26
of avoiding the occurrence of hunting of the cooling water is obtained.
In addition, the actuator for rotationally driving the butterfly valve has
the DC motor, the clutch mechanism and the deceleration mechanism and
drives the butterfly valve on the basis of the aforementioned control signal.
In this case, the high-speed properties of a direct-motor is fully used by
using the DC motor, and the butterfly valve is driven with a sufficient
rotational torque by combining the small sized DC motor and the deceleration
mechanism. Therefore, the overall actuator can be smaller in size.
The return spring propelling the butterfly valve toward the opening
10 state is included and the actuator has the clutch mechanism, whereby the
opening operation of the valve by the return spring in an abnormal state is
smoothly performed.
Moreover, the formation in which the clutch mechanism is placed
between the DC motor and the deceleration mechanism allows the driving
force, namely torque, applied to the clutch mechanism to be decreased
considerably. The sliding and the wear and tear of the clutch mechanism can
be avoided, resulting in mini~tmization of the clutch mechanism as well as the
actuator.
In addition, a cooling control system for an engine according to the
20 present invention, in which a circulating passage of a cooling medium is
formed between a fluid conduit formed in the engine and a fluid conduit
formed in a heat exchanger, and heat generated in the engine is dissipated with
the heat exchanger by circulating the cooling medium in the circulating
passage, includes: a butterfly valve controlling the flow of the cooling medium
25 in the circulating passage between the engine and the heat exchanger in
accordance to the degree of valve opening; a thermo-element for controlling
the degree of butterfly-valve opening responsive to the ch~nging of
temperature, and provided with a heater for heating; and a control unit
generating a control signal for controlling electric energy for heating, which is
30 supplied to the heater provided in the thermo-element, on the basis of at least
the temperature information of the cooling medium.
In this case, it is advisable that the cooling control system for the
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engine according to claim 1, in which the control unit also generates a control
signal for controlling driving of a fan motor that is for forcibly cooling the heat
exchanger. The control unit is added with the engine speed and the load
information regarding the engine, and perfomms a control of the electric energy
for heating, supplied to the heater provided to the thermo-element, and/or a
drive control for the fan motor.
In the preferred embodiment, the control signal for the electric energy
for heating, supplied to the heater provided in the themmo-element, and the
drive control signal for the fan motor are formed with a PWM signal, and a
10 duty value of the PWM signal is changed to control the supplied electric
energy.
The themmo-element is disposed to be in thermal-contact with the
cooling medium, and the degree of butterfly-valve opening is controlled
responsive to the temperature of the cooling medium and the heating of the
15 heater heating in accordance to electric power supplied by the control unit.
Altematively, the themmo-element is disposed to be thermally insulated from
the cooling medium, and the degree of butterfly-valve opening is controlled
responsive to the heating of the heater heating in accordance to electric power
supplied by the control unit.
Preferably, the thermo-element is provided with a wax element
enclosing wax responsive to the temperature of the cooling medium and/or the
heating of the heater, a piston member projected by the wax-element with the
expanding action of the wax in the wax-element, and a cam member carrying
out rotational movement with respect to a shaft with the projecting of the
25 piston member, and the degree of butterfly-valve opening is changed with the
rotational movement of the cam member.
According to the cooling control system as structured thus far, the flow
of the cooling water in the circulating passage between the engine and the heat
exchanger is adjusted by means of the degree of butterfly-valve opening so
30 that the cooling water is controlled to be adjusted to be at an appropliate
temperature. The opening state of the butterfly valve is adjusted by the
thermo-element provided with the heater for heating, so that the degree of
CA 0224208l l998-06-26
12
butterfly-valve opening can be controlled by adjusting electric energy supplied
to the heater in response to the operation state of the engine.
Moreover, as is well-known, the butterfly valve is rotated around the
shaft, thereby the flow can be adjusted and the opening and closing operation
5 is carried out insensitive to the pressure of the cooing water. Therefore, thecooling control system has characteristics that the rotation torque required forthe adjustment of the flow of the cooling water is extremely small.
As a result, comparing with a conventional cooling control system in
which the opening and closing of a poppet valve is controlled with wax as a
10 thermal expansive body, the opening and closing of the valve can be controlled
with small driving force in the cooling control system according to the present
invention, so that elements of mechanical stress can be reduced, resulting in
the improvement of the life and reliability and the reduction in size.
It is should be mentioned that, comparing with a conventional cooling
5 control system in which the degree of butterfly-valve opening is controlled bya stepping motor, the structure in the present invention can be simplified,
resulting in the reduction in costs of the overall device.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a block diagram showing an embodiment when a cooling
control system according to the present invention is applied to an engine for a
vehicle;
Fig. 2 is a block diagram with a partially cross-section of a flow
control unit used in the device in Fig. 1;
Fig. 3 is an enlarged sectional view taken along the A-A' line in Fig. 2;
Fig. 4 is a connection diagram showing a motor drive circuit used in
the device in Fig. 1;
Fig. 5 is a waveform diagram showing an example of a control signal
applied to the motor drive circuit shown in Fig. 4;
Fig. 6 is a block diagram showing a design of an engine control unit
CA 02242081 1998-06-26
(ECU) shown in Fig. 1;
Fig. 7 is a flow chart for explaining the action in ECU;
Fig 8 is a flow chart for mainly explaining the action of a quick
response control continued from the flow chart shown in Fig. 7;
Fig. 9 is a flow chart for mainly explaining the action of a PI control
continued from the flow chart shown in Fig. 7;
Fig. 10 is a flow chart showing an example flow instead of the flow
chart shown in Fig. 8;
Fig. 11 is a block diagram showing an example of a data table used in
10 a process routine shown in Fig. 7;
Fig. 12 is a block diagram showing another example of a data table
used in a process routine shown in Fig. 7;
Fig. 13 is a block diagram showing an example of a data table used in
a process routine shown in Fig. 8;
Fig. 14 is a block diagram showing an example of a data table used in
a process routine shown in Fig. 9;
Fig. 15 is a block diagram showing another example of a data table
used in a process routine shown in Fig. 9;
Fig. 16 is a block diagram showing an example of a data table used in
a process routine shown in Fig. 10;
Fig. 17 is a block diagram showing an example of a data table used in
another embodiment of a cooling control system according to the present
mventlon;
Fig. 18 is a block diagram showing another example of a data table
used in the above embodiment;
Fig. 19 is a block diagram showing another embodiment for a cooling
control system according to the present invention, applied in an engine for a
vehicle;
Figs. 20(a) and 20(b) are block diagrams of a flow control unit in a first
structure used in the system shown in Fig. 19 with a partial cross-section;
Fig. 21 is a block diagram of a flow control unit in a second structure
used in the system shown in Fig. 19 with a partial cross-section;
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Fig. 22 is a block diagram showing a basic design of an engine control
unit (ECU) shown in Fig. 19;
Fig. 23 is a connection diagram showing a PTC heater drive circuit for
driving a PTC heater;
Fig. 24 is a connection diagram showing a motor drive circuit for
driving a fan motor;
Fig. 25 is an explanatory control-process diagram in the use of the flow
control unit in the first structure shown in Figs. 20;
Fig. 26 is an explanatory control-process diagram in the use of the flow
l0 control unit in the second structure shown in Fig. 21;
Fig. 27 is a flow chart for expl~ining the operations performed in ECU;
Fig. 28 is a flow chart continued from the flow chart in Fig. 27 for
explaining the operations performed in ECU;
Fig. 29 is a block diagram showing an example of a conventional
15 cooling system for an engine for a vehicle; and
Fig. 30 is a block diagram with a partially cross section of an example
of a conventional flow control system with a butterfly valve.
DET~I~,F,n DESCRIPTION OF THE PREFERRED
EMBODIMENT(S)
A cooling control system for an engine according to the present
invention will be described below with reference of preferred embodiments
25 shown in the attached drawings.
Fig. 1 shows the overall structure of a cooling control system for an
engine for a vehicle. In Fig. 1, the same reference numerals will be used to
designate the same or similar components as those in the conventional cooling
control system shown in Fig. 29, so that the descriptions of the components
30 and operations will be omitted or simplified as necessary.
As shown in Fig. 1, a flow control unit 11 is connected with a flange to
the outflow-side cooling-water conduit 3a located between the outflow portion
CA 02242081 1998-06-26
ld of the cooling water, placed in the upper portion of the engine, and the
inflow portion 2a of the cooling water placed in the upper portion of the
radiator 2 as the heat exchanger.
As a result, a circulating passage 12 for a cooling medium, namely the
cooling water is formed with including the flow control unit 11.
In the outflow portion ld of the cooling water in the engine 1, a
temperature detecting element 13 such as a thermistor is disposed. A value
detected by the temperature detecting element 13 is converted into data having
a readable form of the control unit (ECU) 15 by a transducer 14, and sent to
10 the control unit (ECU) 15 controlling the operation of the overall engine.
In a preferred embodiment shown in Fig. 1, information regarding the
degree of opening is also sent to the control unit 15 from a throttle position
sensor 17 detecting the degree that a throttle valve 16 of the engine 1 is
opened. Incidentally, although not shown in the drawing, the control unit 15
also receives other information such as the engine speed and so on.
On the other hand, the control signals are sent from the control unit 15
to a motor control circuit 18 and a clutch control circuit 19. The motor controlcircuit 18 and the clutch control circuit 19 control current from the battery 20to supply the control current to a direct-current motor control circuit and a
20 clutch control circuit which are provided in the flow control unit 11 and
described below.
Fig. 2 schematically shows the structure of the aforementioned flow
control unit 11 with a partially cross section. The flow control unit 11
includes a butterfly valve and an actuator for driving the butterfly valve.
The actuator is provided with a direct-current motor 31, in which a
first clutch disc 32a constituting a clutch mechanism 32 is connected to a
rotating shaft 31a of the DC motor 31 in the rotational direction of the rotating
shaft 31a, and attached to slide in the axial direction.
Fig. 3 shows a view taken along the A-A' line in Fig. 2. The rotating
30 shaft 31a of the motor has a hexagonal contour as shown in the drawing. In
the central portion of the first clutch disc 32a, a hexagonal hole is formed to
surround the rotating shaft 31a of the motor.
CA 0224208l l998-06-26
16
Therefore, the first clutch disc 32a is combined in the rotational
direction of the rotating shaft 31a and works to slide in the axial direction.
Returning to Fig. 2, a ring-shaped gutter portion 32b is formed on the
outer circumferential face of the first clutch disc 32a. Into the gutter portion5 32b, an end portion of a working portion 32d of an electromagnetic plunger
32c is loosely inserted. A coil spring 32e is attached to the plunger 32c. In
the normal state in which the plunger 32c is not energized, the first clutch disc
32a is retracted toward the motor 31 by the extending action of the coil spring
32e as shown in Fig. 2.
A second clutch disc 32f is placed opposite the first clutch disc 32a,
and fixed to an input-side rotating shaft 33b constituting a deceleration
mechanism 33.
In the deceleration mechanism 33, the input-side rotating shaft 33b, a
transitional rotating shaft 33c and an output-side rotating shaft 33d are
disposed parallel to each other by bearings located in a case 33a.
On the input-side rotating shaft 33b, a pinion 33e is fixed and meshed
with a spur gear 33f fixed on the transitional rotating shaft 33c. In addition, a
pinion 33g fixed on the transitional rotating shaft 33c is meshed with a spur
gear 33h fixed on the output-side rotating shaft 33d.
The deceleration mechanism 33 has, for example, approximately
one/fiftieth of a deceleration ratio due to the above formation.
The output-side rotating shaft 33d of the deceleration mechanism 33 is
combined with a drive shaft of a flow control valve 34. The flow control valve
34 is provide with a plane-shaped butterfly valve 34b located in a tubular
cooling medium sluice 34a. The butterfly valve 34b is structured so that the
flow of the cooling water is controlled by the angle of the plane direction,
formed by a rotational angle of a shaft 34c as the drive shaft, with respect to
the flowing direction of the cooling water. More specifically, when an angle
of the plane direction of the butterfly valve 34b is approximately zero with
respect to the flowing direction of the cooling water, the valve is opened.
When an angle of the plane direction is approximately perpendicular to the
flowing direction of the cooling water, the valve is closed. The flow of the
CA 02242081 1998-06-26
cooling water is linearly controlled in relation to the angle taken between zeroand 90 degrees.
In the deceleration mechanism 33 side of the shaft 34c, a collar 34d is
secured to the shaft 34c, and a coil shaped return spring 34e is wound on the
5 outer circumference face of the collar 34d. An end of the return spring 34e isengaged with a part of a tubular shaped body constituting the cooling medium
sluice 34a, and the other end of the return spring 34e is engaged with a
projected portion 34f attached to a part of the collar 34d.
In this state, the return spring 34e propels the butterfly valve 34b
l0 combined with the shaft 34c to form the valve opening state.
On the other end portion, opposite from the deceleration mechanism
33, of the shaft 34c, an angle sensor 34g is combined, thereby detecting the
rotational angle of the butterfly valve 34b.
In the flow control unit 11 as structured thus far, the DC motor 31
15 receives drive current from the motor control circuit 18 shown in Fig. 1. Theelectromagnetic plunger 32c of the clutch mechanism 32 receives drive current
from the clutch control circuit 19 shown in Fig. 1. And the data output
regarding the rotational angle of the butterfly valve detected by the angle
sensor 34g is sent to the control unit 15 shown in Fig. 15.
In the structure of Fig. 2, the electromagnetic plunger 32c is energized,
whereupon the working portion 32d moves the first clutch disc 32a toward the
second clutch disc 32f to make a contact state. Upon the drive current being
applied to the DC motor 31, the rotation driving force of the motor 31 is
decreased by the deceleration mechanism, and rotates the butterfly valve 34b
25 through shaft 34c. With the rotation of the shaft 34c, the angle sensor 34g
sends feedback of data regarding the rotational angle to the control unit 15.
Fig. 4 is a connection diagram of the motor control circuit 18. In the
motor control circuit 18, a bridge circuit is formed by a first switching element
Q1 and a second switching element Q2 placed in series between a positive
30 terminal and a negative terminal (earth) of the power (the battery 20), and athird switching element Q3 and a fourth switching element Q4 similarly placed
in series between the positive terminal and the negative terminal.
CA 02242081 1998-06-26
Each switching element is composed of an NPN-type bipolar-transistor.
In consequence, each collector of the first transistor Q1 and the third transistor
Q3 is connected to the positive terminal of the battery 20. Each emitter of the
second transistor Q2 and the fourth transistor Q4 is connected to the earth.
The emitter of the first transistor Q1 and the collector of the second
transistor Q3 are connected and form a first junction 18a. The emitter of the
third transistor Q3 and the collector of the fourth transistor Q4 are connected
and form a second junction 18b.
Between the first junction 18a and the second junction 18b, a pair of
10 drive-current input terminals of the motor 31 are respectively connected.
Control pole terminals of the first transistor Q1 and the fourth
transistor Q4, namely bases are connected to each other and form an input
terminal a. Bases of the second and third transistors Q2 and Q3 are connected
to each other and form an input terminal b.
Fig. S shows switch control signals alternatively sent from the control
unit 15 to the input terminal a and the input terminal b of Fig. 4.
The control signal is formed with a waveform by PWM, and drives at
a fixed time period in response to the rotational direction of the motor. In
closing the valve, the control signal having a longer pulse width (W1) is sent
20 only to the input terminal a. In opening the valve, the control signal having a
shorter pulse width (W2) is sent only to the input terminal b.
When the butterfly valve 34b is to be opened, the return spring 34e is
efficiently driven with the shorter pulse width using torque in the returning
direction thereof.
Where the butterfly valve 34b is to be closed, the switch control signal
having the pulse width shown as (a) in valve closing in Fig. S is sent to the
terminal a of Fig. 4. Therefore, the transistors Q1 and Q4 are ON-controlled
by the switch control signal corresponding to the pulse width shown as (a) in
Fig. S, and the motor 31 is rotationally driven in a direction.
Where the butterfly valve 34b is to be opened, the switch control
signal having the pulse width shown as (b) in valve opening in Fig. S is sent tothe terminal b of Fig. 4. Therefore, the transistors Q2 and Q3 are ON-
CA 02242081 1998-06-26
19
controlled by the control signal of the pulse width shown as (b) in Fig. 5, and
the motor 31 is rotationally driven in the reverse direction.
Fig. 6 shows a basic design of the ECU 15 shown in Fig. 1. The ECU
15 includes a signal processing part 15a for converting a signal, sent from each5 sensor, to a digital signal recognizable by the ECU; a comparison part 15b forcomparing the input data processed in the signal processing part 15a with
various data stored in a table form in a memory part 15c; and a signal
processing part 15d for computing the compared result by the comparison part
15b and oll~pullillg it as the control signal.
The operation of the cooling control system for the vehicle engine
shown in Fig. 1 to Fig. 6 will be explained below with reference to control
flows mainly performed by the ECU 15 shown in Fig. 7 and the following
drawings.
Referring the flow of Fig. 7, the vehicle engine is started, whereupon
the control signal is sent from the ECU 15 to the clutch control circuit 19,
whereby the drive current is applied to the electromagnetic plunger 32c shown
in Fig. 2, and the clutch mechanism 32 is in the transmissive state.
At this time, the ECU 15 sends the control signal for closing a flow
control valve, namely the butterfly valve 34b in the valve opening state, to the20 motor control circuit 18 (step S1).
As a result, the control signal having the pulse width (W1) shown as
the valve closing state in Fig. 5 is added to the terminal a in the motor control
circuit 18 in Fig. 4, whereby the DC motor 31 is rotationally driven, and the
butterfly valve 34b is temporally closed through the deceleration mechanism
25 33.
In step S2, the ECU 15 reads an initial engine-starting cooling-water
temperature (Tws) from the transducer 14 receiving the information from the
temperature detecting element 13. Continuously, in step S3, the ECU 15
fetches the engine speed (N), the degree of throttle opening (~T) and a
30 cooling-water temperature (Tw).
After that, in step S4, the relationship between the cooling-water
temperature (Tw) and the cooling-water temperature in engine starting (Tws)
CA 02242081 1998-06-26
is determined. That is to say, when the condition of Tw>Tws is determined to
be NO, the flow goes to step S5. Here, the control signal is sent to the motor
control circuit 18, and an angle of valve is set so that the detected angle by the
angle sensor 34g is to be approximately 90 degrees. Thereby, the butterfly
5 valve 34b retains the valve closing state (step S6).
In step S7, whether the engine is stopped or not is determined and
when the engine (NO) is determined to not be stopped, a routine of relu~ g
to step S3 is repeated thereafter. In step S7, when the stopping of the engine
(YES) is determined, the flow shifts to step S8. Here, the ECU 15 stops to
send the control signal to the clutch control circuit 19, and the operation of the
electromagnetic plunger 32c is stopped.
As a result, the clutch mechanism 33 is released and the butterfly valve
34b is to be in a valve opening state due to the action of the return spring 34e.
Returning to step S4, the condition of Tw>Tws is determined to be
15 YES, whereupon the flow goes to step S9. Here, a target setting water-
temperature (Ts) corresponding to the engine speed (N) - the degree of throttle
opening (~T) as the load information of the engine is retrieved from a table (~;)
shown in Fig. 11.
On the table (~) shown in Fig. 11, the target setting water-temperature
20 (Ts) is written in matrix between the engine speed (N) and the degree of
throttle opening (~T). Incidentally, for convenience in writing in the drawing,
the relationship between the engine speed (N) and the degree of throttle
opening (~T) is roughly written greatly, but actually, they are written in detail.
Even when they are written somewhat roughly, in an intermediate value,
25 interpolation is carried out so that the practically useful target setting water-
temperature (Ts) can be obtained. This is similar to each table referred
hereafter.
In step S10, a temperature deviation (~T = Tw-Ts) is computed from
the cooling-water temperature (Tw) and the target setting water-temperature
30 (Ts) retrieved from table (~) shown in Fig. 11. In step S11, a reference
control-valve angle (~so) corresponding to the engine speed (N) and the
degree of throttle valve (~T) is retrieved from table (~) shown in Fig. 12.
CA 02242081 1998-06-26
In step S12, a temperature deviation velocity (Tv) is computed from
the last water-temperature (Two) and the now water-temperature (Tw). More
specifically, the computing process of Tv = ~T/~t = (Two-Tw)/sec as shown
in step S12 of Fig. 7 is performed.
In step S13, two data of the temperature deviation (~T) and the
temperature deviation velocity (Tv) which are respectively obtained in steps
S10 and S12 are respectively performed with a comparative computation with
a predetermined temperature deviation value (~TA) and a predetermined
temperature deviation velocity value (Tv). That is to say the comparative
10 computation of ~T _ ~TA, Tv _ TvA as shown in Fig. 7 is carried out.
In table (~) described below, the predetermined temperature deviation
value (~TA) and the predetermined temperature deviation velocity value (Tv)
are defined as relatively lower values of deviation components boxed with
bolded lines. The values less than the predetermined values are determined in
step S13 (NO), whereupon the flow goes to step S21 shown in Fig. 8.
Steps S21 to S25 shown in Fig. 8 are a routine of a quick response
control for relatively quickly performing the flow control for the cooling waterwith the flow control valve.
In step S21, a control-valve setting angle (~s) corresponding to the
20 temperature deviation (~T) obtained in step S10 and the temperature deviationvelocity (Tv) obtained in step S12 is retrieved from the table (~) shown in Fig.13.
In table (~) shown in Fig. 13, the control-valve setting angles (~s) are
written in matrix between the temperature deviation (~T) and the temperature
25 deviation velocity (Tv) similar to the tables (~) and (~). A range (~4) of a
smaller value of the temperature deviation (~T) and a range (Tv4) of a smaller
value of the temperature deviation velocity (Tv) which are boxed with bolded
lines in the table (~) are defined as the predetermined temperature deviation
value (~TA) and the predetermined temperature deviation velocity value (Tv).
In step S22, the computation for a combined control-valve angle (H) is
performed. This is the computation of ~ = ~so~ ~s performed between the
reference control-valve angle (~so) retrieved in step S11 and the control-valve
CA 02242081 1998-06-26
22
setting angle (Hs) retrieved in step S21.
In step S23, the computation for selecting a rotational direction of the
motor, namely the computation of ~ 3v-~ is performed. A value ~v used
in this computation is obtained from the angle sensor 34g detecting the
5 control-valve angle shown in Fig. 2. The rotational direction of the motor is
decided on the basis of a negative value or a positive value resulted by the
- above computation.
Continuously, in step S24, the drive of the DC motor, namely a direct-
current motor 31 shown in Fig. 2 is carried out. In this point, a duty pulse is
produced in response with the obtained value ~, in which a lar~e duty pulse
is produced when the value ~H is large and a small duty pulse is produced
when the value ~ is small, and the DC motor is driven by the PWM signal.
Thereby, the butterfly valve 34b as the flow control valve is rotated in
step S25. After the routine explained thus far, the flow goes back to step S7 inFig.7.
As a result of the comparative computation in step S13 in Fig. 7, upon
the temperature deviation (~T) and the temperature deviation velocity (Tv)
being determined to be below the predetermined range (YES), the flow moves
to step S31 in Fig. 9.
Steps S31 to S40 shown in Fig. 9 are a routine for performing a PI
control including an integral control element which allows the flow control of
the flow control valve for the cooling water to change at unit-times
continuously and slightly.
In step S31, a proportional valve of the degree of valve opening (Hsp)
is retrieved from table (~) of proportional vales for the degree of valve opening
(~sp) corresponding to the temperature deviation (~T) as shown in Fig. 14.
In step S32, an integral value for the degree of valve opening (~si) is
retrieved from table (~) of integral values of the degree of valve opening (Hsi),
shown in Fig. 15, corresponding to the temperature deviation (~T).
Upon going to step S33, whether or not a value of the temperature
deviation velocity (Tv) obtained in step S21 is "zero" is determined. In this
point, the value of the temperature deviation velocity Tv is determined to be
CA 02242081 1998-06-26
23
"zero", whereupon the flow moves to step S37 explained below. When the
value of the temperature deviation velocity Tv is determined not to be "zero",
the flow goes to step S34.
In step S34, the determination as to the value of the temperature
5 deviation ~T found in step S10 is carried out. The flow goes to step S35 when
~T>zero is determined in step S34, step S36 when ~T<zero is determined,
and step S37 when ~T = zero is determined.
In step S35, a value ~ for decreasing the degree of control-valve
opening is computed as the computation for the degree of control-valve
10 opening. The computation for ~ = ~so-(~sp+Hsi) is performed with the
reference degree of control-valve opening ~so retrieved in step S 11, the
proportional value for the degree of valve opening ~sp retrieved in step S31,
and the integral value for the degree of valve opening ~si retrieved in step S32.
In step S36, a value for increasing the degree of control-valve opening
15 is computed as the computation for the degree of control-valve opening. The
computation for H = Hso+(~sp+~si) is performed.
And, in step S37, a process for using the last control-valve angle ~ as it
is is performed.
Going to step S38, the computation for ~ v-~ is performed with
20 the control-valve angles (~) respectively found in step S35 to step S37 and the
degree of control-valve opening (~v) obtained from the control-valve angle
sensor 34g. The rotational direction of the motor is decided as a result of the
computation.
By processing step S39 and step S40, the degree of flow-control-valve
25 opening is controlled. The actions in step S39 and step S40 are the same as
that in step S24 and step S25, so that the explanation is omitted.
Returning to step S7 in Fig. 7 after the above routine, the routine thus
far is repeated until the engine is stopped.
Through the processes explained thus far, the temperature of the
30 cooling water is conducted in a state that the ch~nging of temperatures of the
cooling water is forecast with the load information with respect to the engine.
According to the circumstances, the flow control valve is controlled to be
CA 02242081 1998-06-26
24
closed and opened by the control signal obtained by the first control-signal
generating mode and the second control-signal generating mode, resulting in
the improved responsibility of the control valve and the further enhanced
precision of controlling the cooling water.
In the flow shown in Fig. 7 to Fig. 9, in order to improve the
responsibility of the flow control valve, the degree of control-valve opening ~sset according to the temperature deviation ~T and the temperature ch~nging
velocity Tv is read and the degree of control-valve opening is controlled. A
flow shown in Fig. 10 can be used for further simplifying the above manner.
In Fig. 10, step S13 in Fig. 7 and steps S21 to S25 in Fig. 8 are
transposed.
More specifically, step S51 in Fig. 10 is the same as step S13 in Fig. 7.
When NO is determined in step S51, in step 52, a control valve angle ~s'
corresponding to the engine speed (N)-the degree of throttle opening (~T) as
15 the load information of the engine is retrieved from table (~) shown in Fig. 16.
In step S53, the computation for selecting the rotational direction of
the motor, namely, the computation for ~ = Hv-~s' similar to the case of step
S23 is performed. The rotational direction of the motor is decided according
to a positive value or a negative value as a result of the computation.
The processes of step S54 and step S55 are the same as that of step
S24 and step S25, so that the explanation is omitted.
Moving step S56, whether or not the degree of flow-control-valve
opening ~v obtained from the angle sensor 34g is equal to the control-valve
setting angle ~s' found in step S52 (~s' = ~v ?) is determined. When unequal
25 (NO) is determined, the flow returns to step S7 in Fig. 7. When equal (YES)
is determined, the flow goes to step S31 in Fig. 9 to perform the PI control.
In either of the thus far explained flows shown in Fig. 7 to Fig. 9 and
shown in Fig. 10, an angle of the butterfly valve 34b as the flow control valve
is obtained as the degree of flow-control-valve opening ~v from the angle
30 sensor 34g, but a similar control can be performed without the use of the
degree of flow-control-valve opening ~v.
More specifically, where the angle sensor is used, basically, the degree
CA 02242081 1998-06-26
of flow-control-valve opening ~v can be received as a control deviation signal
and a temperature can be controlled to be the target setting water-temperature
Ts. Where the angle sensor is not used, the DC motor can be controlled with
the PI duty pulse drive on the basis of the temperature deviation signal ~T
5 directly.
In consequence, in the state that the control-valve angle sensor is not
used, the control is performed by replacing table ~) shown in Fig. 13 with a
table of DC motor drive PI duty values, thereby obt~ining the same result.
Fig. 17 shows an example of a proportional duty table corresponding
lO to the temperature deviation signal ~T, used in the above manner. Fig. 18
shows an example of an integral duty table corresponding to the temperature
deviation signal ~T, used in the above manner.
Referring to the corresponded tables, a duty ratio of the PWM signal
added to the bridge type DC motor drive circuit shown in Fig. 4 is time-
15 controlled, thereby obt~ining the same effects.
In the control unit 15, upon the actual cooling-water temperature Tw
obtained from the temperature detecting element 13 and the target setting
water-temperature Ts, when a value ~T as the difference is larger than a
predetermined value, namely is out of a range of predetermined temperatures,
20 after a fixed time, an abnormal condition output can be generated.
By generating the abnormal condition output, the clutch control circuit
19 controls the clutch mechanism 32 to release, whereby the butterfly valve
34b can results in the valve opening state through the action of the return
spring 34e. Therefore, the circulation of the cooling water is stimulated and
25 the overheat of the engine can be avoided.
Although the description thus far has been referred to the preferred
embodiment in which the cooling control system according to the present
invention is applied to the engine for the vehicle, the present invention is notintended to be limited to the particular preferred embodiment, and can be
30 applied to another engine and the same effects are obtained thereby.
Next, a second embodiment of the cooling control system for the
CA 02242081 1998-06-26
26
engine will be described below.
In this structure, a PWM signal for a PTC-heater heating control is
applied from the ECU 15 to a PTC drive circuit 18 described below. A PWM
signal for a fan-motor drive control is applied from the ECU 15 to a fan-motor
5 drive circuit 19 described below. The PTC drive circuit 18 and the fan-motor
drive circuit 19 control the current supplied from the battery 20 with each
PWM signal, and control current (electric power) is applied to the fan motor
and a PTC heater provided in a flow control unit 111 and described below.
Figs. 19 show a first structure of the flow control unit 111 with a
lO cross-section. In the flow control unit 111, a cylinder portion 131 connectedtoward the engine is provided. In the lower portion of the cylinder portion 131,a shaft 132 is disposed at the central area, and a butterfly valve 133 rotatablysupported by the shaft 132 is located. The butterfly valve 133 is in the closingstate as shown in Fig. 20(a) by a return spring (not shown) disposed on the
15 shaft 132 while a thermo-element, described below, is not being operated. In
the opening state of the butterfly valve 133, a valve seat 134 formed of a
flexible material and placed in the lower portion of the cylinder portion 131 isin contact with a valve body.
The valve body of the butterfly valve 133 is formed in a disc shape as
20 well-known, and the flow of the cooling water is controlled by the angle of the
plane direction of the valve body, formed by a rotational angle of the shaft 132,
with respect to the flowing direction of the cooling water. More specifically,
when an angle of the plane direction of the valve body is approximately zero
with respect to the flowing direction of the cooling water, the valve is opened.25 When an angle of the plane direction is approximately perpendicular to the
flowing direction of the cooling water, the valve is closed. The flow of the
cooling water is approximately linearly controlled in relation to the angle taken
between zero and 90 degrees.
A thermo-element 135 is placed in the cooling-water outflow side,
30 namely the radiator side of the butterfly valve 133. In an example shown in
Fig. 20, the thermo-element 135 is placed in the cooling water in the cooling-
water conduit 3a so as to be in thermal-contact with the cooling water.
CA 02242081 1998-06-26
In the thermo-element 135, a tubular wax-element 136 enclosing wax
as a thermal expansive body is disposed to locate in the cooling water. In the
wax-element 136, a piston member 137 embedded to move in a vertical
direction in accordance to the degree of wax expanding is placed.
On the upper portion of the piston member 137, a cylindrical retainer
138 is disposed to surround the piston member 137. The retainer 138 is
abutted to a cam member 139 placed on the same axis as that of the shaft 132
by upward movement of the piston member 137, and rotated about the shaft
132.
With the rotation of the cam member 139 by the working of the piston
member 137, the butterfly valve 133 is opened as shown in Fig. 20(b), and the
cooling water circulates.
A ring-shaped PTC heater 140 including a thermistor, having the
positive temperature coefficient character, as a heating element is placed to
15 circle the wax-element 136. On and beneath the PTC heater 140, a pair of
ring-shaped electrodes 141 and 142 for applying current to the PTC heater 140
is placed. Current flows from a socket 143 formed on a side face of the flow
control unit 111 through a lead wire to the electrodes 141 and 142.
In consequence, the aforementioned wax-element 136 is heated by
20 energizing the PTC heater 140 via the socket 143. Then, as described
hereinbefore, the piston member 137 is projected upward by the thermal
expansion of wax enclosed in the wax-element 136, and the butterfly valve
133 is opened.
According to the flow control unit 111 in the first structure shown in
25 Figs. 20, the degree that the butterfly valve 133 is opened can be controlled in
accordance to the temperature of the cooling water and the electric energy
applied to the PTC heater.
Fig. 21 shows a second structure of the flow control unit 111 with a
cross-section. Incidentally, in Fig. 21, the same reference numerals will be
30 used to designate the same components as those in Fig. 20, so that the in-depth
description will be omitted.
The thermo-element 135 in the flow control unit 111 shown in Fig. 21
CA 02242081 1998-06-26
28
is thermally insulated from the cooling water. For this reason, a wall portion
144 cutting off the thermo-element 135 from the heat of the cooling water is
disposed in the exit side of the butterfly valve 133. The disc-shaped PTC
heater 140 is sandwiched between the disc-shaped electrodes 141 and 142 and
5 placed in the bottom portion of the thermo-element 135.
The wall portion 144 is formed of materials such as synthetic resin,
thereby thermal insulating properties are enhanced.
Fig. 21 shows the closing state of the butterfly valve 133. Upon
energizing the PTC heater 140, the piston member 137 is projected upward by
10 the thermal expansion of wax enclosed in the wax-element 136. The butterfly
valve 133 is opened by the same action as that of the case explained in Fig.
20(b).
According to the flow control unit 111 in the second structure shown
in Fig. 21, the degree that the butterfly valve 133 is opened is controlled in
15 accordance to the electric energy applied to the PTC heater irrelevant of the temperature of the cooling water.
Fig. 22 shows a basic design of ECU 115 shown in Fig. 19. The ECU
115 includes a signal processing part 115a for converting a signal, sent from
each sensor, to a digital signal recoganizable by the ECU; a comparison part
20 115b for comparing the input data processed in the signal processing part 115a
with various data, described hereinafter, stored in a table form in a memory
part 115c; and a signal processing part 115d for colllpulillg the compared
result by the comparison part 115b and outputting it as the control signal. The
PWM signals outputted from the signal processing part 115d are sent to a PTC
25 drive circuit 118 and a fan-motor drive circuit 119 shown in Fig. 23 and Fig. 24.
The PTC drive circuit 118 shown in Fig. 23 includes an NPN-type
transistor 118b. The PWN signal outputted from the above signal processing
part 115d is sent through a base input resistor 118a into a base of the transistor
30 118b. A collector of the transistor 118b is connected to the battery through
the PTC heater 140 placed in the flow control unit 111, and an emitter is
connected to a reference point of potential (a body of the vehicle). A diode
CA 02242081 1998-06-26
29
118c for protection is connected in shunt with respect to the PTC heater 140.
As shown as PWM land PWM 2 in Fig. 23, a pulse signal for a heater
heating control in which a duty value is controlled is sent from the ECU 115 to
the base of the transistor 118b. Therefore, the transistor 118b passes current
5 to the PTC heater 140 in response to the duty value of the pulse signal,
whereby a heat value of the PTC heater 140 is controlled.
Similarly, the fan-motor drive circuit 119 shown in Fig. 24 includes a
NPN type transistor 119b. The PWN signal outputted from the above signal
processing part 115d is sent through a base input resistor 19a into a base of the
10 transistor 119b. A collector of the transistor 119b is connected to the battery
through the fan motor 6b, and an emitter is connected to the reference~ point ofpotential (a body of the vehicle).
Similar to PWM land PWM 2 shown in Fig. 23, a pulse signal for a
fan-motor control in which a duty value is controlled is sent from the ECU 115
15 to the base of the transistor 119b. Therefore, the transistor 119b passes
current to the fan motor 6b in response to the duty value of the pulse signal,
whereby the rotational speed of the fan motor 6b is set and the dissipation
efficiency by the radiator is controlled.
Operation in the first structure of the flow control unit (Fi 20)
The operation using the first structured flow control unit shown in Fig.
20 in which the degree of butterfly-valve opening is controlled in response to
the temperature of the cooling water and the electric energy supplied to the
PTC heater will be below with reference to the control processes shown in Fig.
25.
An example of Fig. 25 shows the case that the cooling-water
temperature at the exit of the engine is controlled to be within a predeterminedrange. With a target setting temperature Ts for the cooling-water temperature
at the exit of the engine, in process K1, a deviation ~T (= Two-Ts) between
the target setting temperature Ts and a cooling-water temperature Two
obtained from the temperature sensor 13 measuring the cooling-water
temperature at the exit of the engine is computed.
CA 02242081 1998-06-26
In process K2, the amount of element lift required to the thermo-
element 135 in accordance to the above deviation ~T is computed. In this
point, the amount of element lift is roughly decided by the cooling-water
temperature Two, the flow of the cooling water (dependent upon the engine
speed), and the duty value of the PWM signal for energizing the PTC motor.
And, the duty value of the PWM signal for energizing the PTC motor is
decided by these parameters.
Note that computation of the well-known PID (the amount of follow-
up control) is used in the case of the determination of the duty value of the
lO ~WM signal. In many cases, a control with only the aforementioned
parameters cannot be performed due to various disturbance elements in
actuality. Therefore, in order to correct delay in time of control system,
minute correction in the positive-negative direction is added to the duty vale of
the PWM signal.
The PWM signal for the PTC-heater heating control is sent to the PTC
drive circuit 118 shown in Fig. 23, whereby the PTC heater heats in process
K3, and the thermo-element is lifted in process KS. In this case, as explained
hereinafter, another requirement regarding the amount of element lift is added
in process K4.
In process K6, mechanical linear movement is converted into rotational
movement through the cam due to the element lift. More specifically, the shaft
132 of the butterfly valve 133 is rotated. The return spring is disposed on the
shat 132 of the butterfly valve as described hereinbefore. In process K7, the
return element by the return spring is incorporated, and in process K8, the
25 opening and closing operation of the butterfly valve is carried out.
In process K9, the flow of the cooling water flowing into the radiator is
changed. As shown in process K11, the temperature of the cooling water at
the entrance of the engine is changed. In this case also, as explained
hereinafter, another requirement is added in process K10 for ch~nging the
30 temperatures of the cooling water.
In process K12, the temperature of the cooling water is changed by the
heat exchange while the cooling water is passing through the engine, and
CA 0224208l l998-06-26
31
results in the temperature at the exit of the engine.
At this time, in the first structured flow control unit, the thermo-
element 135 simultaneously receives the heating action by the PTC heater 140
and the action by the temperature of the cooling water, resulting in the element5 lift. In other words, the temperature at the exit of the engine acts on the
thermo-element as shown in process K13. In process K4, an amount of heat
(the temperature and the flow) in process K13 is added to an amount of heat
by the PTC heater, whereby the amount of element lift is determined.
The temperature of the cooling water at the exit of the engine is
l0 detected by the temperature sensor as shown in process K14. In process K1,
the detected temperature at the exit is added as a negative factor with respect
to the target setting temperature Ts, and the deviation ~T is generated.
In process K15, the hlro~ ation of the deviation ~T used for
com~ulillg the duty value of the PWM signal corresponding to the rotational
15 speed of the fan motor that drives the radiator fan. In this case, the
computation of PID is used similarly to process K2.
The PWM signal for driving the fan motor which is generated as
explained thus far is supplied to the fan-motor drive circuit 119 shown in Fig.
24, so that the rotational speed of the radiator fan is adjusted (changed) as
20 shown in process K16. In this case, as shown in process K17, elements such
as the ch~nging of air-speed caused by vehicle speed, and the ch~nging of
outside-air-temperature being incorporated, a cooling effect by the radiator is
changed as shown in process K18. The elements of the cooling efficiency
incorporate into the ch~n~ing element of the flow of the cooling water flowing
25 into the radiator in the aforementioned process K10, and acts on the changing of the temperature at the entrance of the engine.
Operation in the second structure of the flow control unit (Fi~. 21)
The operations using the second structured flow control unit shown in
30 Fig. 21 in which the degree of butterfly-valve opening is controlled in response
to the electric energy supplied to the PTC heater, independent from the
temperature of the cooling water, will be explained below with reference to
CA 02242081 1998-06-26
the control processes shown in Fig. 26.
Similar to the former example, an example of Fig. 26 shows the case
that the cooling-water temperature at the exit of the engine is controlled to bewithin a predetermined range. In processes K1 to K18 shown in Fig. 26, the
5 same reference numerals are used to designate the same processes as those
shown in Fig. 25, so that the overlapped explanation is omitted.
In the flow control unit in the second structure shown in Fig. 21, the
thermo-element 135 is disposed to be thermally insulted from the cooling
water as described hereinbefore, therefore a process indicated with K13 is
lO substantially deleted comparing with the example shown in Fig. 25. That is,
the process in which the temperature at the exit of the engine acts on the
thermo-element is deleted.
In process K4 of Fig. 26, the outside air temperature acts on the
thermo-element 135, so that the element of the outside air temperature is
15 incorporated with respect to an amount of heat by the PTC heater, and the
amount of element lift is decided.
The cooling device according to the present invention carries out the
cooling operation with the control processes explained thus far and shown in
Fig. 25 and Fig. 26. A flow of the control mainly performed by the ECU 115
20 which is shown in Fig. 27 and Fig. 28 will be explained below. Incidentally,
the control flow shown in Fig. 27 and Fig. 28 mainly corresponds to K1 to
K15 of the control processes shown in Fig. 25 and Fig. 26. The control using
the flow control unit in the first structure (Fig. 20) and the control using theflow control unit in the second structure (Fig. 21) have a slightly different
25 control-flow from each other, so both control flows will be separately
explained below.
Control flow in usin the flow control unit in the first structure (Fi~.
In step S101 of Fig. 27, the ECU 115 reads an opening-valve start
temperature To (from 70~C to 80~C) of the thermo-element. In step S102, the
ECU 115 detects the engine speed N; the degree of throttle opening ~T,
CA 02242081 1998-06-26
outputted from the throttle opening-level sensor 17 detecting the negative
pressure P of the intake air as the engine-load information; and the cooling-
water temperature Tw from the temperature sensor 13.
In step S103, the ECU reads a target setting water-temperature Ts of
5 the cooling water at the exit of the engine, written with the relationship
between the engine speed N and the degree of throttle opening ~T, from a
table stored in the memory part 115c shown in Fig. 22. Continuously, in step
S104, the ECU computes a deviation ~T (=Ts-Tw) between the target setting
water-temperature Ts read from the above table and the cooling-water
lO temperature Tw from the temperature sensor 13, detected in step S102.
In step S105, with the opening-valve start temperature To of the
thermo-element, obtained in step S101, and the cooling-water temperature Tw
detected in step S102, the ECU determines whether or not the condition is
Tw<To. Where the result is NO, the flow moves to step S106. This means
15 the state in which an actual measured value Tw of the cooling water equals tothe opening-valve start temperature To by the thermo-element or in which the
cooling-water temperature w is higher than the opening-valve start temperature
To by the thermo-element.
In step S106, whether of not the condition is ~T = Ts-Tw<zero is
20 determined with the deviation ~T computed in step S104. When the condition
is YES, the flow goes to step S107. This means the state in which the target
setting water-temperature Ts equals to the actual cooling-water temperature
Tw or in which the actual cooling-water temperature Tw is higher than the
target setting water-temperature Ts, therefore the cooling water is needed to
25 be cooled quickly.
In step S107, after receiving the above condition, the ECU performs a
step for generating the PWM signal for driving the fan motor 6b. More
specifically, a duty value is retrieved from a table written thereon with the
temperature deviation ~T computed in step S104 and DF (the engine speed
30 NF~ being the duty value of the PWM signal corresponding to the temperature
deviation ~T, and the PWM signal corresponding to the retrieved duty value is
produced. The PWM signal is supplied to the fan-motor drive circuit 119
CA 02242081 1998-06-26
34
shown in Fig. 24, whereby the fan motor 6b is driven to rotate.
Continuously, in steps S108 and S109, a step for generating the PWM
signal for controlling electric power supplied to the PTC motor is performed.
More specifically, in step S108, a duty value Don is retrieved from a duty
5 value Do table, written thereon with duty values to obtain the setting water-
temperature Ts, with respect to the relationship between the engine speed N
and the degree of throttle opening ~T obtained in step S102.
Going to step S109 of Fig. 28, the computation of PID is performed.
More specifically, a proportional duty value Dpn is retrieved from a table
O written thereon with proportional duty values of the PWM signal for driving
the PTC heater which corresponds to the temperature deviation ~T, and an
integral duty value Din is retrieved from a table written thereon with integral
duty values of the PWM signal for driving the PTC heater which corresponds
to the temperature deviation ~T.
In step S110, the computation for D = Don+(Dpn+Din) is performed
so as to find a duty value D of the PTC drive pulse from the duty value,
obtained in step S108, and the proportional duty value Dpn and the integral
duty value Din retrieved in step S109.
In step S111, the PWM signal of the duty value D is sent to the PTC
20 drive circuit 118 shown in Fig. 23. The current controlled by the duty value D
is applied to the PTC heater 140, so that the thermo-element 135 is heated in
response to the volume of current (electric energy) supplied, and the amount of
lift ~LH of the thermo-element 135 is decided in step S112.
In using the first structured flow control unit shown in Fig. 20, the
25 thermo-element 135 senses the cooling-water temperature, and the amount of
element lift is controlled with the cooling-water temperature in parallel with
the actions caused by the aforementioned steps. In step S113 shown in Fig. 28
subsequent to reference letter E of Fig. 27, the amount of thermo-element lift
~Lw caused by the cooling-water temperature Tw acts, and is added to the
30 amount of lift ~LH of the thermo-element 135 which is decided in step S112.
As shown in step S114, the combined amount of thermo-element lift ~L is
defined as ~L = ~LH+~Lw.
CA 02242081 1998-06-26
Based on the combined amount of lift ~L, the butterfly valve 133 is
rotationally driven in step S115, and the degree of butterfly-valve opening is
defined as Hv. The flow returns from step S115 through reference letter C of
Fig. 27 to step S102 and circulates.
As shown in step S116, the flow of the cooling water is controlled, and
the cooling-water temperature at the exit is controlled to converge on the
target setting water-temperature Ts eventually.
The explanation thus far shows the control flow when the cooling
water is needed to be cooled in the state that the cooling-water temperature is
lO higher than a predetermined temperature in step S106.
Another control flow in a state other than the aforementioned state will
be explained. When the determination in step S106 is NO, that is when the
actual cooling-water temperature Tw is lower than the target setting water-
temperature Ts, the flow goes into the routine of step S117. In step S117, the
motor driving the radiator fan turns off. In step S118, the duty value of the
PWM signal for controlling current applied to the PTC motor is defined as
zero. In other words, in this case, the flow moves to step S111 via reference
letter B shown in Fig. 27 and Fig. 28, and the current applied to the PTC
motor is in a breaking state. Therefore, the radiator fan 6b stops and also the
20 heating of the PTC heater 140 stops, so that the butterfly valve 133 is
propelled toward the direction of valve closing. Thereby, until the actual
cooling-water temperature Tw exceeds the target setting water-temperature Ts,
the dissipation efficiency is decreased to rapidly increase the cooling-water
temperature.
When the actual measured value Tw of the cooling-water temperature
is lower than the opening-valve start temperature To by the thermo-element in
step S105, that is when the determination is YES, the flow goes into the
routine of step S119. The duty value of the PWM signal for controlling
current applied to the PTC heater is defined as zero. In this case, the flow
30 goes to step S111 via reference letter C shown in Fig. 27 and Fig. 28. The
current applied to the PTC heater is in the breaking state. Therefore, the
heating of the PTC heater is stopped so as to increase the cooling-water
CA 02242081 1998-06-26
36
temperature rapidly.
Control flow in using the flow control unit in the second structure (Fig.
The control flow with the use of the second structured flow control
unit shown in Fig. 21 in which the degree of butterfly-valve opening can be
controlled mainly in accordance to electric energy applied to the PTC heater
and independent from the temperature of the cooling water is explained below.
In the control flow, a routine formed with reference letter E in the flow
chart shown in Fig. 27 and Fig. 28 is omitted substantially. More specifically,
the amount of thermo-element lift ~LH caused by the cooling-water
temperature Tw does not act in step S113, so that the control is performed
with only the amount of thermo-element lift ~LH dependent upon the PTC
heater shown in step S112.
According to the cooling control system in the embodiments described
thus far, the target setting water-temperature is derived from parameters such
as the engine speed and the load information (the degree of throttle opening
~3T), and the deviation of the cooling-water temperature with respect to the
target setting water-temperature is computed, and then the amount of current
supplied to the PTC heater for heating the thermo-element is controlled. As a
result, the opening state of the butterfly valve is controlled and the dissipation
efficiency of the cooling water is controlled. In addition, the rotation of the
fan motor is controlled, so that an appropriate temperature for operating the
engine is ensured all the times.
In the flow chart of Fig. 27 and Fig. 28, it is explained that the tables
stored data are constructed and the required data is read from the table, but the
data may not necessarily be stored in a table form. The data can be fetched by
the computing processes.
The embodiments where the cooling control system of the present
invention is applied to the engine for the vehicle have been described, but the
present invention is not intended to be limited to a specific use as described
hereinbefore, and the same action and effects can be obtained if the present
CA 02242081 1998-06-26
37
invention is applied to another engine.
As is clear from the aforementioned description, according to a cooling
control system and a cooling control method relating to the present invention,
5 a target setting temperature of a cooling medium is found on the basis of loadinformation regarding at least an engine, and a temperature deviation and a
ch~nging velocity of the temperature deviation are found from the target
seKing temperature and an actual temperature of the cooling medium, so that
an appropriate control form can be selected on the basis of the found values.
A PI control is performed as a first control signal generating mode and
a quick response control is performed as a second control signal generating
mode, so that the temperature conduct with high precision can be performed
while the ch~nging of the temperature of the cooling water is being forecast.
In consequence, the occurrence of hunting of the temperature of the
15 cooling water is avoided, resulting in the improved fuel efficiency and the
decrease of hazardous exhaust fumes.
An actuator controlling a flow control means is composed of a direct-
current motor, a clutch mechanism and a deceleration mechanism, so that the
overall actuator is small in size while drive torque of the flow control means is
20 obtained sufficiently, in which when it is employed for an engine for a vehicle,
the occupied volume is decreased.
In addition, with using a return spring propelling the flow control
means in an opening direction of the valve, disadvantages such as the overheat
of the engine that is caused by the occurrence of trouble are prevented, and a
25 fail-safe function is exploited.
Moreover, the cooling control system for an engine according to the
present invention is characterized by adopting a conformation in which a
butterfly valve is driven with a thermo-element, and structuring that the degreeof butterfly-valve opening is controlled by heating the thermo-element on the
30 basis of the operation parameters of the engine.
In consequence, as described in "SUMMARY OF THE
INVENTION",'the characteristics of the butterfly valve which is capable of
CA 02242081 1998-06-26
extremely decreasing rotation torque for adjusting the flow of the cooling
water is used, so that there is no element of mechanical stress, resulting in the
improved life of the device and reliability.
It should be mentioned that the structure of the overall system can be
5 simplified, thereby achieving the cooling control system-with the reduction of costs.
